<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  
</head>

<body>
  <div id="app">
      <div :style="sty"></div>
      <div :style="{width: a, height:100+500+'px',background:'purple'}"></div>
  </div>
  <script src="./vue.js"></script>
  <script>
    const vm = new Vue({
      el: '#app',
      data: {
        sty:{
          width: '200px',
          height: '200px',
          background: 'red'
        },
        a: '200px',
      }
    })
  </script>
</body>

</html>